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3 * Portions Copyright (C) 1996-2001, 2003 Internet Software Consortium.
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50 * Permission to use, copy, modify, and distribute this software for any
51 * purpose with or without fee is hereby granted, provided that the above
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58 * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
59 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL DIGITAL EQUIPMENT
60 * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
61 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
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67 #if defined(LIBC_SCCS) && !defined(lint)
68 static const char sccsid[] = "@(#)res_query.c 8.1 (Berkeley) 6/4/93";
69 static const char rcsid[] = "$Id: res_query.c,v 1.11 2008/11/14 02:36:51 marka Exp $";
70 #endif /* LIBC_SCCS and not lint */
71 #include <sys/cdefs.h>
72 __FBSDID("$FreeBSD$");
74 #include "port_before.h"
75 #include <sys/types.h>
76 #include <sys/param.h>
77 #include <netinet/in.h>
78 #include <arpa/inet.h>
79 #include <arpa/nameser.h>
88 #include "port_after.h"
90 /* Options. Leave them on. */
96 #define MAXPACKET PACKETSZ
98 #define MAXPACKET 1024
102 * Formulate a normal query, send, and await answer.
103 * Returned answer is placed in supplied buffer "answer".
104 * Perform preliminary check of answer, returning success only
105 * if no error is indicated and the answer count is nonzero.
106 * Return the size of the response on success, -1 on error.
107 * Error number is left in H_ERRNO.
109 * Caller must parse answer and determine whether it answers the question.
112 res_nquery(res_state statp,
113 const char *name, /*%< domain name */
114 int class, int type, /*%< class and type of query */
115 u_char *answer, /*%< buffer to put answer */
116 int anslen) /*%< size of answer buffer */
118 u_char buf[MAXPACKET];
119 HEADER *hp = (HEADER *) answer;
124 oflags = statp->_flags;
127 hp->rcode = NOERROR; /*%< default */
129 if (statp->options & RES_DEBUG)
130 printf(";; res_query(%s, %d, %d)\n", name, class, type);
133 n = res_nmkquery(statp, QUERY, name, class, type, NULL, 0, NULL,
136 if (n > 0 && (statp->_flags & RES_F_EDNS0ERR) == 0 &&
137 (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC|RES_NSID))) {
138 n = res_nopt(statp, n, buf, sizeof(buf), anslen);
139 if (n > 0 && (statp->options & RES_NSID) != 0U) {
141 n = res_nopt_rdata(statp, n, buf, sizeof(buf), rdata,
142 NS_OPT_NSID, 0, NULL);
148 if (statp->options & RES_DEBUG)
149 printf(";; res_query: mkquery failed\n");
151 RES_SET_H_ERRNO(statp, NO_RECOVERY);
155 n = res_nsend(statp, buf, n, answer, anslen);
158 /* if the query choked with EDNS0, retry without EDNS0 */
159 if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U &&
160 ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0) {
161 statp->_flags |= RES_F_EDNS0ERR;
162 if (statp->options & RES_DEBUG)
163 printf(";; res_nquery: retry without EDNS0\n");
168 if (statp->options & RES_DEBUG)
169 printf(";; res_query: send error\n");
171 RES_SET_H_ERRNO(statp, TRY_AGAIN);
175 if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
177 if (statp->options & RES_DEBUG)
178 printf(";; rcode = (%s), counts = an:%d ns:%d ar:%d\n",
186 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);
189 RES_SET_H_ERRNO(statp, TRY_AGAIN);
192 RES_SET_H_ERRNO(statp, NO_DATA);
198 RES_SET_H_ERRNO(statp, NO_RECOVERY);
207 * Formulate a normal query, send, and retrieve answer in supplied buffer.
208 * Return the size of the response on success, -1 on error.
209 * If enabled, implement search rules until answer or unrecoverable failure
210 * is detected. Error code, if any, is left in H_ERRNO.
213 res_nsearch(res_state statp,
214 const char *name, /*%< domain name */
215 int class, int type, /*%< class and type of query */
216 u_char *answer, /*%< buffer to put answer */
217 int anslen) /*%< size of answer */
219 const char *cp, * const *domain;
220 HEADER *hp = (HEADER *) answer;
221 char tmp[NS_MAXDNAME];
223 int trailing_dot, ret, saved_herrno;
224 int got_nodata = 0, got_servfail = 0, root_on_list = 0;
229 RES_SET_H_ERRNO(statp, HOST_NOT_FOUND); /*%< True if we never query. */
231 for (cp = name; *cp != '\0'; cp++)
232 dots += (*cp == '.');
234 if (cp > name && *--cp == '.')
237 /* If there aren't any dots, it could be a user-level alias. */
238 if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL)
239 return (res_nquery(statp, cp, class, type, answer, anslen));
242 * If there are enough dots in the name, let's just give it a
243 * try 'as is'. The threshold can be set with the "ndots" option.
244 * Also, query 'as is', if there is a trailing dot in the name.
247 if (dots >= statp->ndots || trailing_dot) {
248 ret = res_nquerydomain(statp, name, NULL, class, type,
250 if (ret > 0 || trailing_dot)
252 if (errno == ECONNREFUSED) {
253 RES_SET_H_ERRNO(statp, TRY_AGAIN);
256 switch (statp->res_h_errno) {
261 if (hp->rcode == SERVFAIL)
267 saved_herrno = statp->res_h_errno;
272 * We do at least one level of search if
273 * - there is no dot and RES_DEFNAME is set, or
274 * - there is at least one dot, there is no trailing dot,
275 * and RES_DNSRCH is set.
277 if ((!dots && (statp->options & RES_DEFNAMES) != 0U) ||
278 (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0U)) {
281 for (domain = (const char * const *)statp->dnsrch;
286 if (domain[0][0] == '\0' ||
287 (domain[0][0] == '.' && domain[0][1] == '\0'))
290 if (root_on_list && tried_as_is)
293 ret = res_nquerydomain(statp, name, *domain,
300 * If no server present, give up.
301 * If name isn't found in this domain,
302 * keep trying higher domains in the search list
303 * (if that's enabled).
304 * On a NO_DATA error, keep trying, otherwise
305 * a wildcard entry of another type could keep us
306 * from finding this entry higher in the domain.
307 * If we get some other error (negative answer or
308 * server failure), then stop searching up,
309 * but try the input name below in case it's
312 if (errno == ECONNREFUSED) {
313 RES_SET_H_ERRNO(statp, TRY_AGAIN);
317 switch (statp->res_h_errno) {
326 * This can occur due to a server failure
327 * (that is, all listed servers have failed),
328 * or all listed servers have timed out.
329 * ((HEADER *)answer)->rcode may not be set
330 * to SERVFAIL in the case of a timeout.
332 * Either way we must return TRY_AGAIN in
333 * order to avoid non-deterministic
335 * For example, loaded name servers or races
336 * against network startup/validation (dhcp,
337 * ppp, etc) can cause the search to timeout
338 * on one search element, e.g. 'fu.bar.com',
339 * and return a definitive failure on the
340 * next search element, e.g. 'fu.'.
343 if (hp->rcode == SERVFAIL) {
344 /* try next search element, if any */
349 /* anything else implies that we're done */
353 /* if we got here for some reason other than DNSRCH,
354 * we only wanted one iteration of the loop, so stop.
356 if ((statp->options & RES_DNSRCH) == 0U)
361 switch (statp->res_h_errno) {
366 if (hp->rcode == SERVFAIL)
374 * If the query has not already been tried as is then try it
375 * unless RES_NOTLDQUERY is set and there were no dots.
377 if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0U) &&
378 !(tried_as_is || root_on_list)) {
379 ret = res_nquerydomain(statp, name, NULL, class, type,
385 /* if we got here, we didn't satisfy the search.
386 * if we did an initial full query, return that query's H_ERRNO
387 * (note that we wouldn't be here if that query had succeeded).
388 * else if we ever got a nodata, send that back as the reason.
389 * else send back meaningless H_ERRNO, that being the one from
390 * the last DNSRCH we did.
393 if (saved_herrno != -1)
394 RES_SET_H_ERRNO(statp, saved_herrno);
396 RES_SET_H_ERRNO(statp, NO_DATA);
397 else if (got_servfail)
398 RES_SET_H_ERRNO(statp, TRY_AGAIN);
403 * Perform a call on res_query on the concatenation of name and domain,
404 * removing a trailing dot from name if domain is NULL.
407 res_nquerydomain(res_state statp,
410 int class, int type, /*%< class and type of query */
411 u_char *answer, /*%< buffer to put answer */
412 int anslen) /*%< size of answer */
415 const char *longname = nbuf;
419 if (statp->options & RES_DEBUG)
420 printf(";; res_nquerydomain(%s, %s, %d, %d)\n",
421 name, domain?domain:"<Nil>", class, type);
423 if (domain == NULL) {
425 * Check for trailing '.';
426 * copy without '.' if present.
430 RES_SET_H_ERRNO(statp, NO_RECOVERY);
434 if (n >= 0 && name[n] == '.') {
435 strncpy(nbuf, name, n);
442 if (n + d + 1 >= MAXDNAME) {
443 RES_SET_H_ERRNO(statp, NO_RECOVERY);
446 sprintf(nbuf, "%s.%s", name, domain);
448 return (res_nquery(statp, longname, class, type, answer, anslen));
452 res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) {
453 char *file, *cp1, *cp2;
457 if (statp->options & RES_NOALIASES)
461 file = getenv("HOSTALIASES");
462 if (file == NULL || (fp = fopen(file, "re")) == NULL)
465 buf[sizeof(buf) - 1] = '\0';
466 while (fgets(buf, sizeof(buf), fp)) {
467 for (cp1 = buf; *cp1 && !isspace((unsigned char)*cp1); ++cp1)
472 if (ns_samename(buf, name) == 1) {
473 while (isspace((unsigned char)*++cp1))
477 for (cp2 = cp1 + 1; *cp2 &&
478 !isspace((unsigned char)*cp2); ++cp2)
481 strncpy(dst, cp1, siz - 1);